Some substrate process chambers utilize a process kit that includes a cover ring disposed above a dielectric deposition ring. The cover ring includes a central opening through which an exposed substrate is processed. The inventors have observed that the grounding condition (e.g., electrically grounded or floating) of the cover ring may influence a processing profile of the substrate proximate an edge of the substrate. For example, the cover ring may be grounded via physical contact of the ring to a grounded chamber component (e.g., a shield) during some processes to facilitate process uniformity at the edge of the substrate. However, the inventors have discovered that for processes utilizing power provided in a VHF range (e.g., greater than about 30 MHz), the existing physical contact between the ring and process chamber components is not sufficient to electrically ground the ring, resulting in an increase in electrical potential of the ring, and thus, process non-uniformities across the substrate.
Therefore, the inventors have providing an improved process kit for substrate process chambers.